Process of extruding steel



2,767,837 Patented Oct. 23, 1956 257675837 .PROGESS OF .STEEL Elliot S. Nachtman, Park .Forest,,and Eldon B. Moore, Calumet .City, 11]., assignors to La Salle Steel Company, Hammond, Ind., a corporation of Delaware N Drawing. Application June 27, 1955, .Serial No. 518,411

7 Claims. (Cl. 207-10) This invention relates to a metallurgical process for producing steels having new and improved physical and mechanical properties, including improved strength properties, and it relates further to a new and improved steel product which is produced by same.

This application is a continuation-in-part of our copending applications Ser, No.s293,43l, filed..lune 13 1952, and entitled Metallurgical Process and Steel Products Produced Therefrom, and Ser. No. 293,432, filed June 13, 1952, and entitled Metallurgical Process and Steel Products Produced Therefrom, both now abandoned.

It is an object of this invention to produce a steel having new and improved physical and mechanical properties and it is a related object to provide a method for producing steels of the type described in a simple and eflicient manner and in a single operation concurrent with the working of thesteelgto eifect reduction in cross-sectional area. as by advancing the steel through .a die for extrusion or drawing.

it has been found, in accordance with this invention, that with which also harden by the practice of steels that strain harden and precipitation, hereinafter referred to as precipitation hardening, at temperatures below the lower critical temperature for the steel composition, the

-physical and mechanical properties of-the steel, including tensile strengths, yield strengths, hardness, impact strengths and the like can be improved by working the steel, as by drawing or extrusion through a suitable die to effect reduction in cross-sectional area, when the steel is heated fordrawing to a temperature above 200 F. up to the lower critical temperature for the steel composi tion. It the steel shows hardening characteristics 'because of precipitation hardening or other re-arrangement,

then .it becomes possible by the process described and claimed in this invention to improve the strength properties of the steel and to improve the combination of strength and elastic limit by drawing the steel, even in the relatively low temperature range of 200-450 F., without des troyingor impairing others of the desirable properties of the steel.

Representative of the steels whichexhibit the desired characteristics for use in the improvementofthemechanical and strength properties by the practice of this invention are the plain carbon steels and the low alloy, low and medium carbon steels of the non-austenitic type having a pearlitic structure in a matrix of free ferrite.

Operation within the range of 200450 F. before appreciable precipitation occurs provides improvedstrength properties with still excellent elastic properties. "In addition to the marked increase which is secured in the strength properties of the steel by the rnetallurgical process of working the steel through a die,as1by drawing or by extrusion while the steel is at the described elevated temperature, marked improvements vare securedgin hardness. The steels produced have better machinability and greater wear resistance depending upon the composition of the steel, residual stresses are relieved or;may themon- .450" F. and 60,0"

trolled to give better control of the warpage and cracking increases with heavier drafts. In effect, it has become possible by the simple medium of working the steel through .a die toeffect reduction in cross-sectional area While the steel is heated to an elevated temperature to produce a readily available steel at low cost having properties which .enablesubstitution ,of the steel for the m re expensive heat treated steels or the less :available and more expensive alloy steels. Thus, .in one step, it is possible by .the process described to produce .a steel having properties which .areequal to or exceed the properties of steels which have heretofore required a series of processing steps to build ,up the desired properties in the metalproduchusuallyat the expense of other properties. It is possible .ufor thefirst time to make useof a low cost and readily available steel and to introduce therein properties which enable use of the steel vor other more eX- p as v al y s e l To the best of our knowledge, no one before has ever recognized the possibility of achieving such modification physicaland mechanical propert e of steel and to ,control the development of those properties for tailoring th st el far rti u a us vs m b h use Qf r a t as which t kerlace u on w k n h met at elevated temperatures and under the pressure conditions existing upon deformation during passage through the die. It is this concept which .is believed to represent an advance of the extreme importance in the field of metallurgy and particularly in the processing of steels for use.

The tie-in between precipitation hardening and the development of the described properties in steel upon working through a die at elevated temperatures to elfect reduction in cross-sectional area is incapable for the present, of being clearly explained. It is known that the mechanical and physical properties of the steel are markedly increased -by working such steels through a die at temproperties is more gradual than in the range above 450 F. to 850 R, .as defined in our copending applications filed concurrently herewith. Between the range of above R, which is within the blue-brittle range, the steels produced have less ductility although they develop marked improvements in strength properties. These steels are suitable for many particular types of applications. The ductility :is maximized and the corresponding improvements in mechanical and physical properties are secured along with improvements in surtace smoothness and machinability when the steel is processed at a temperature within the range of GOO-850 F. Above 850 ,F., ,the strength properties of the steel begin to fall off slightly from the maximum-butmarked reductions are reflected in residual stresses such that it becomes possible to produce a type ofstee'l havinkphysical andimechanical properties far superior to that secured by steels drawn at room temperature, such as defined in a third application filed concurrentlyjherewith. When the steels drawn at a temperature above 850 F. are cooled .down rapidly immediately afterdrawing, a new and novel condition is developed in the steel'wherein compressive stresses dominate in the surface portions, as distinguished from tensile stresses,

The method of heating to introduce the desired temperature into the steel for drawing is unimportant. Heating may be achieved in many well known systems such as in an electric furnace, by resistance heating or by immersion of the steel into a hot or molten bath of metal salts and the like. For example, the steel may be heated by means of a salt bath which may effectively be used also to coat the metal with a lubricant and otherwise condition the surface of the steel for in the copending application of Nachtman, Ser. No. 286,039, filed on May 3, 1952, wherein description is made that, in the past, the metal has been prepared for deformation to produce a better finish in a cold finishing operation by treating the surface of the metal first with an acid to remove scale, followed by a rinse to remove acid, followed further by liming to protect the surface and to prepare the surface for subsequent application of lubricant prior to cold working or drawing. The improvement described in the aforementioned copending application resides in the development of a process wherein the various steps of descaling, washing, liming and lubricating are provided in a single step wherein the steel is treated with a molten bath of sodium hydroxide and a reducing agent wherein the steel is descaled by chemical reduction and wherein the steel is heated to the desired temperature for advancing the steel through the die to effect reduction in cross-sectional area in accordance with the practice of this invention.

The following examples are given by way of illustration of the improvements which are secured in steels drawn at elevated temperatures within the range de-- scribed wherein the steel compositions are defined by the major ingredients other than iron.

EXAMPLE 1 Steel composition:

.16 percent carbon .71 percent manganese .010 percent phosphorus .030 percent sulphur .25 percent silicon 45 Table I.5 percent reduction Tensile Yield Elong. Izod Strength, Strength, 1%", Warpage Impact, p. s. 1. p. s. 1. percent Factor 20 F.

Ft. Lbs.

Hot Rolled Mate- 65 77, 750 73, 750 19 640 23 77, 750 74, 000 19 669 18 79, 000 75,000 22 680 20 80,000 77,000 20 +.636 N. B. so. 000 77,000 19 597 17 7 0 83, 750 81, 250 16. 5 626 22. 7 83,000 80,000 17. 5 528 N. A. 88, 500 87,000 16 531 3. 6 86, 750 84, 500 16 600 3. 5

N. A.-Not available. N. B.-Not a clean break test.

drawing, as described Table Il.-30 percent reduction Tensile Yield Elong. Izod Strength, Strength, 1%, Warpage Impact, p. s. i. p. s. 1 percent Factor 20 F., Ft. Lbs.

Hot Rolled Mate- N. B.Not a clean break test.

EXAMPLE 2 Steel cornpostion:

.44 percent carbon 1.52 percent manganese .018 percent phosphorus .310 percent sulphur .29 percent silicon Procedure.-The procedure for test corresponds with 0 that described in Example 1.

Table III.5 percent reduction Tensile Yield Elong. Izod Strength, Strength, 1%", Warpage Impact, p. s. i. p. s. i. percent Factor F., Ft. Lbs.

Hot Rolled Material 113, 500 76, 250 032 N. B

18 591 N. B. 12. 5 650 N. B. 10 636 8. 0 017 7. 0

N. B.Not a clean break test.

Table I V.-3 0 percent reduction Tensile Yield Elong. Izod Strength, Strength, 1%", Warpage Impact, p. s. i. p. s. i. percent Factor F., Ft. Lbs.

N. B.-Not a clean break test.

EXAMPLE 3 .42 percent carbon .87 percent manganese .016 percent phosphorus .026 percent sulphur .29 percent silicon .87 percent chromium .20 percent molybdenum 7 5 that described in Example 1.

:Table V.=.-'-5 percentreduction Tensile Yield Elcng. Izod Strength, Strength, 1%", "Warpage "Impact, -p..s.i. p. s. i. v:percent Factor 20 F., .Ft. Lbs.

Hot Rolled 7 Material. 146, 260 102, 000" 17.5 016 6.7 -Te nip. of Draw,

--Table VI 30 percent reduotzon Tensile. Yield .E long. Izod Strength, Strength, 1%, v Warpage Impact, p. s. i. p. s. i. percent Factor 20 F.,

1 Ft. Lbs

Hot Rolled Material 146, 250 102,000 17.5 +.016 6.7 Temp. of Draw,

= 8 +.-459 2.6 .9 +.52s, 4.3 *9 +.488 4.7 9 497j 5.0 5. +.4s1 5. 7 '9 +.392' 4.0

In the remainder of the examples the procedure was substantially similar to that of Example '1 except that in a number of instances indicated in the tables, the amount of draft was other than 5 or 30percent.

EXAMPLE .4

,Steel composition:

.39 percent carbon .76 percent manganese .015 percent phosphorus .019 percent sulphur v.28 percent silicon 1.80 percent nickel .76 percent chromium .25 percent molybdenum Table VII-30 percent reduction Tensile Yield Elong. Izod Strength, Strength, 1%, Warpage Impact, p. s. i. p. s. 1. percent Factor 20 F., I l5. Lbs.

Hot Rolled Material 98,250 60,000 29 +.042 15.3 Temp. of Draw,

EXAMPL 5 :Stcelcomposition:

.63 percent .carbon '.92 percent manganese .021 percent phosphorus .025 percent sulphur 529 percent isilicon 1831percent chromium l'able .1VIH...-'25 percent reduction Tensile Yield Elong. Izod Strength, Strength, 2", Warpage Impact, p.,s.i. p.s.,-1'. percent Factor 20 F., 5 1.1.1.118.

Hot Rolled -Material 146,750 89,500 13 +.02s 3.3 T%1p. of Draw, w 170, 250 156,000 7 +212 2 178,000 172,500 .9 +.254 2 187,500 180,000 5 +243 2 178,500 169,000 ,9 +..136 2 174,250 150,000 10 +.143 3.3

. EXAMPLE .6

Steel composition:

.50 percent carbon .78 percent manganese .010 percent phosphorus .021 percent sulphur .30 percent silicon 1.01 percent chromium .12 percent vanadium Table IX-+ percent reduction Tensile Yield ,Elong. :Izod Strength, Strength, 1%, Warpage Impact, p. s. i. p. s..i. percent Factor -1201F., Ft. Lbs. V3

0 Hot Rolled Mat erial 92,000 45,000 29.0 010 17.7 Temp. of Draw,

4 N. A.'N0t available.

EXAMPLE 7 Steel composition:

.39 percent carbon .92 percent manganese .014 percent phosphorus .044 percent sulphur .22 percent silicon .45 percent nickel .45 percent chromium .19 percent molybdenum Table X-35 percent reduction Tensile Yield 'Elong. 'Warpage .strength, strength, 1%, Factor p. s. i. p. s. 1. percent Hot Rolled Material 124, 330 110,800 20 -.004 Temp. of Drew, F;

765 EXAMPLE -8 Steel composition:

.41 percent carbon .81 percent manganese .012 percent phosphorus .033 percent sulphur .26 percent silicon .30 percent nickel .20 percent chromium .10 percent molybdenum .0008 percent beryllium reduction of area properties proved steel product having 'Table XI-25 percent reduction It will be apparent from the foregoing tables that marked improvements are secured in the tensile strength and in the yield strength properties of the various steels when drawn at an elevated temperature above 200 F. especially when taken in comparison with the corresponding strength properties of the same steel drawn through a drawing die at room temperature to effect an equivalent reduction in cross-sectional area. As illustrated by elongation, it will be apparent that the ductility of the steels, which is good when drawn in the described temperature range, decreases in the range of 450600 F. and that the ductility returns and in most instances is improved along with the improvements in physical properties when the steel is drawn at a temperature beyond 600 F. The improvement in strength properties secured by the practice of this invention together with good elongation and provides a new and imcharacteristics capable of use where it was required to employ the more expensive alloy steels or to make use of steels which have been subjected to multiple steps such as heat treatments subsequent to forming.

It will be apparent from the foregoing that we have provided a new and improved metallurgical process by which the physical and mechanical properties of steels can be modified by improvement in the reaction which takes place as the steel is worked under pressure and at elevated temperature during deformation as the steel passes through a die to etfect reduction in cross-sectional area. Thus it has become possible selectively to introduce improved characteristics in steels in a single operation coincident with the working of the steel to efiect reduction in cross-sectional area thereby to achieve in one step that which has in some instances been unobtainable heretofore and in many other instances only approached by such multiple operations as successive reductions alone or in combination with heat treatment or strain relieving.

In the processing of steels to improve physical properties, in accordance with the invention described and claimed in the instant case and as described and claimed in the other copending applications filed concurrently herewith and entitled Method of Working Non-Austenitic Steels and Products Produced By Same, Metallurgical Process for Steels and Products Produced By Same, and Method of Working Steels and Products Produced By Same, it is believed that the improvements in tensile strength can be related to the chemistry of the steel, the amount of reduction and the temperature of the steel being drawn in accordance with the following equation:

I T.S. +T.S.= (1+percent reduction) X CD ETD (650XC+90XMn+4XCXMn+1000XP+Z) wherein T.S. CD

temperature of drawings in equals tensile strength of the steel due to elevated temperature of drawing, C equals carbon content in percent 100, Mn equals manganese content in percent)( 100, P equals phosphorus content in percentx 100, T equals R, X equals temperature at Y in the curve, Y equals vertex of the curve for the steel at various percent reductions, and Z is an empirical factor for the particular steel.

The following will illustrate the application of this equation to a particular set of conditions.

A steel of the composition of Example 1 is given a 5 percent reduction at 560 F. Applying the figures to the equation, the resulting tensile strength of the steel may be calculated as follows:

T.S.-i-T.S.=1.05X (650X 16+90X71+ CD ETD T.S.+T.S.=87,753 p. s. i. GD ETD In the above equation the vertex of the curve for 5 percent reduction for the steel is at about 12,550 pounds per square inch above the tensile strength of the material drawn at room temperature. The temperature at the vertex is about 520 F. These figures were used for X and Y in the above equation.

The experimental value of 86,750 pounds per square inch as set forth in Table I compares with the calculated values of 87,753.

The following will illustrate the calculations when the same steel is drawn to effect a 30 percent reduction at 450 F.

The vertex of the curve for the 30 percent reduction is about 17,250 pounds per square inch above the tensile strength of the material drawn at room temperature. This equals Y. The peak of the 30 percent curve ap pears to be at about 545 F. This equals X. Z for the steel composition is 51,500 as used in the previous equation.

The following is the calculation to determine the tensile strength of the particular steel drawn under the above conditions:

T.S. +T.S. (1 +percent reduction) X (650X C+ CD ETD XMn+4 GXMn+ 1000 P+Z)+ T.S. +T.S. =95,984+ 13,427 CD ETD 450 F. T.S.+T.S.=l09,411 p. s. i. CD ETD The calculated value of 109,411 pounds per square inch compares with the experimental tensile strength of 109,000 in Table II.

It will be understood that changes may be made in the details of formulation and methods of prooesing without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1. The metallurgical process for the improvement of mechanical and physical properties of hot rolled steel while maintaining good ductility, which strain hardens and hardens by some mode of precipitation during working at a temperature between ZOO-450 F., comprising the steps of descaling the steel and lubricating the surfaces of the steel, and advancing the hot rolled steel through a die to effect reduction in cross-sectional area while the steel is at a temperature within the range of 200-450 F.

2. The metallurgical process for the improvement of mechanical and physical properties of hot rolled steel while maintaining good ductility, which strain hardens and hardens by some mode of precipitation during working at a temperature between 200-450 F., comprising the steps of descaling the steel and lubricating the surfaces of the steel, and drawing the hot rolled steel through a draw die to effect reduction in cross-sectional area while the steel is at a temperature within the range of 200450 F.

3. The metallurgical process for the improvement of mechanical and physical properties of hot rolled steel while maintaining good ductility, which strain hardens and hardens by some mode of precipitation during working at a temperature between 200-450" F. comprising the steps of descaling the steel and lubricating the surfaces of the steel, and extruding the hot rolled steel through a die to effect reduction in cross-sectional area while the steel is at a temperature within the range of ZOO-450 F.

4. The metallurgical process comprising drawing a non-austenitic hot rolled steel which strain hardens and hardens by some mode of precipitation during working at a temperature between 200-450" F. and which has a pearlitic structure in a matrix of free ferrite to effect reduction in cross-sectional area while the steel is at a temperature within the range of ZOO-450 F. whereby improvements are secured in the physical and mechanical properties of the steel and descaling and lubricating the hot rolled steel prior to the drawing step.

7 properties produced by the process of claim 1.

process for producing the properties of cold finished, hot rolled steel bars having improved mechanical and physical properties while maintaining ductility and wherein the hot rolled steel bars strain harden and harden by some mode of precipitation 6. In a metallurgical when worked at a temperatur between 200450 F., the

steps of descaling the steel bars and lubricating the surfaces of the steel bars, and advancing the steel bars through a die to eifect reduction in cross-sectional area while the steel is at a temperature within the range of ZOO-450 F. a

7. In a metallurgical process for producing the properties of cold finished, hot rolled steel bars having improved mechanical and physical properties while maintaining ductility and wherein the hot rolled steel bars strain harden and harden by some mode of precipitation when worked at a temperature between 200-450 F., the steps of descaling the steel bars and lubricating the surfaces of the steel bars, and drawing the steel bars through a draw die to efiect reduction in cross-sectional area while the steel is at a temperature within the range of 200-450 F.

References Cited in the file of this patent UNITED STATES PATENTS Buchholtz May 8, 1934 Young Apr. 28, 1942 OTHER REFERENCES July 1946, pages 

1. THE METALLURGICAL PROCESS FOR THE IMPROVEMENT OF MECHANICAL AND PHYSICAL PROPERTIES OF HOT ROLLED STEEL WHILE MAINTAINING GOOD DUCTILITY, WHICH STRAIN HARDENS AND HARDENS BY SOME MODE OF PRECIPITATION DURING WORKING AT A TEMPERATURE BETWEEN 200-450* F., COMPRISING THE STEPS OF DESCALING THE STEEL AND LUBRICATING THE SURFACES OF THE STEEL, AND ADVANCING THE HOT ROLLED STEEL THROUGH A DIE TO EFFECT REDUCTION IN CROSS-SECTIONAL AREA WHILE THE STEEL IS AT A TEMPERATURE WITHIN THE RANGE OF 200-450* F. 